Fuzion • Fuzion Design • Type Syntax Sugar

Type Syntax Sugar

Even though types such as array, choice, function types, are mapped to Fuzion features, it could improve readability and usability a lot to have special syntax for declaration of these types and their instances.

is type	Feature	Type Declaration		value syntax sugar	comment
is type	Feature	verbose	syntax sugar	value syntax sugar	comment
sequence, list or array	`Sequence`	`Sequence A`	`[T]`	`[a,b,c]` `[]`	A value `[a,b,c]` is an instance of `array T` (that can be assigned to type `Sequence T`), while type `[A]` is equivalent to `Sequence T`. The type of a sequence value is inferred from the target it is assigned to, or, if the target does not have a declared type, from the first element in the sequence (`[void]` for an empty sequence).
dictionary, map	`Map`	`Map A B`	`[A => B]`	`[a1 => b1, a2 => b2, a3 => b3]`	A map value is of type `ordered_map`, the elements must inherit `ordered`.
function or lambda	`Function`	`Function R A B` `Function R A` `Function R`	`(A,B) -> R` `A,B -> R` `(A) -> R` `A -> R` `() -> R`	`(a,b) -> f a b` `a,b -> f a b` `(a) -> f a` `a -> f a` `() -> f const`	A lambda value must be assigned to a field of a function type.
tagged union	`choice`	`choice A B C`	`A \| B \| C`	`a`	A value `a` of type `A` will be converted to a choice type `A \| B \| C` implicitly in an assignment to a field whose type is the choice type.
tuple	`tuple`	`tuple A B C`	`(A, B, C)`	`(a, b, c)` `()`	Note that `(a)` is _not_ a one-tuple. The type of `()` is `unit`, which is an heir of `tuple`. Tuple syntax is also used for destructuring as in `(x, y) := point`.

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